Bacillus thuringiensis has been widely used for 40 years as a safe biopesticide for controlling agricultural pests and mosquitoes because it produces insecticidal crystal proteins. However, spores have also been shown to contribute to overall entomopathogenicity. Here, the opportunistic properties of acrystalliferous B. thuringiensis Cry N and Bacillus cereus strains were investigated in an insect species, Galleria mellonella, and in a mammal, BALB/c mice. In both animal models, the pathogenicity of the two bacterial species was similar. Mutant strains were constructed in which the plcR gene, encoding a pleiotropic regulator of extracellular factors, was disrupted. In larvae, coingestion of 10 6 spores of the parental strain with a sublethal concentration of Cry1C toxin caused 70 % mortality whereas only 7 % mortality was recorded if spores of the ∆plcR mutant strain were used. In mice, nasal instillation of 10 8 spores of the parental strain caused 100 % mortality whereas instillation with the same number of ∆plcR strain spores caused much lower or no mortality. Similar effects were obtained if vegetative cells were used instead of spores.The cause of death is unknown and is unlikely to be due to actual growth of the bacteria in mice. The lesions caused by B. thuringiensis supernatant in infected mice suggested that haemolytic toxins were involved. The cytolytic properties of strains of B. thuringiensis and B. cereus, using sheep, horse and human erythrocytes and G. mellonella haemocytes, were therefore investigated. The level of cytolytic activity is highly reduced in ∆plcR strains.Together, the results indicate that the pathogenicity of B. thuringiensis strain 407 and B. cereus strain ATCC 14579 is controlled by PlcR.

The genomic sequences of Salmonella enterica subsp. enterica strains CT18, Ty2 (serovar Typhi), and LT2 (serovar Typhimurium) were analyzed for potential variable number tandem repeats (VNTRs). A multiplelocus VNTR analysis (MLVA) of 99 strains of S. enterica supsp. enterica based on 10 VNTRs distinguished 52 genotypes and placed them into four groups. All strains tested were independent human isolates from France and did not reflect isolates from outbreak episodes. Of these 10 VNTRs, 7 showed variability within serovar Typhi, whereas 1 showed variability within serovar Typhimurium. Four VNTRs showed high Nei's diversity indices (DIs) of 0.81 to 0.87 within serovar Typhi (n ‫؍‬ 27). Additionally, three of these more variable VNTRs showed DIs of 0.18 to 0.58 within serovar Paratyphi A (n ‫؍‬ 10). The VNTR polymorphic site within multidrugresistant (MDR) serovar Typhimurium isolates (n ‫؍‬ 39; resistance to ampicillin, chloramphenicol, spectinomycin, sulfonamides, and tetracycline) showed a DI of 0.81. Cluster analysis not only identified three genetically distinct groups consistent with the present serovar classification of salmonellae (serovars Typhi, Paratyphi A, and Typhimurium) but also discriminated 25 subtypes (93%) within serovar Typhi isolates. The analysis discriminated only eight subtypes within serovar Typhimurium isolates resistant to ampicillin, chloramphenicol, spectinomycin, sulfonamides, and tetracycline, possibly reflecting the emergence in the mid-1990s of the DT104 phage type, which often displays such an MDR spectrum. Coupled with the ongoing improvements in automated procedures offered by capillary electrophoresis, use of these markers is proposed in further investigations of the potential of MLVA in outbreaks of salmonellosis, especially outbreaks of typhoid fever.

Although B. mallei MICs are often lower, the overall results underline the importance of resistance in both species. The susceptibilities measured are consistent with the current recommendations for the treatment of B. pseudomallei and B. mallei infections.

Ninety-six isolates of Bacillus anthracis recovered in France between 1994 and 2000 were tested for their susceptibilities to 25 different antibiotics. Resistance to penicillin G and amoxicillin was 11.5%. All of the isolates were resistant to cotrimoxazole and susceptible to doxycycline, ciprofloxacin, pefloxacin, levofloxacin, teicoplanin, vancomycin, clindamycin, imipenem, and rifampin.Bacillus anthracis is an aerobic rod-shaped organism that is the causative agent for anthrax. Humans can be infected after contact with infected animals or their waste products. When anthrax affects humans, it is usually from an occupational exposure, and the cutaneous form represents the majority of cases (95%) (6). Infections usually respond well to prompt antibiotic treatment. The intestinal form is rare and follows the ingestion of food contaminated by spores (14). This form is characterized by an acute inflammation of the intestinal tract, and initial symptoms include nausea, vomiting, and fever. These symptoms are followed by abdominal pain, vomiting of blood, and severe diarrhea. Intestinal anthrax results in death in 25 to 60% of cases. The respiratory form follows the inhalation of spores and is characterized by an abrupt clinical onset with mild fever and malaise. The first stage of infection, lasting from hours to a few days, involves flu-like symptoms including fever, coughing, weakness, and chest pain. The second stage of inhalation infection usually ends in death within a period of days (1, 13). Despite their gravity, both intestinal and respiratory infections can be treated by early intravenous administration of antibiotics and intensive supportive care. Without immediate treatment, inhalation anthrax is usually fatal.Recent events have demonstrated that the major threat of B. anthracis is connected to bioterrorism and biological warfare. Spores produced in dry form can be spread by means of letters or aerosols (2). As all incidents must be treated as real until proven otherwise, there is a necessity for a rapid and effective antibiotic prophylaxis. Doxycycline and ciprofloxacin are effective antibiotic choices for treatment; however, resistance to these antibiotics has been previously described (4, 10). Moreover, the inappropriate use of these drugs may result in the emergence of antibiotic-resistant strains in naturally acquired disease.The aim of this study was to determine the in vitro susceptibilities of 96 isolates of B. anthracis recovered in France to 25 different antibiotics in order to expand the choices for effective antibiotic treatment. One strain was isolated from a human source, 28 were isolated from animal sources, and 67 were isolated from environmental sources. Phenotypic identification was done by a routine laboratory technique: Gram staining, motility, and hemolysis on blood agar. Biochemical identification was performed by using the Biolog (Hayward, Calif.) system with the dangerous pathogens database. Genotypic characterization was performed by using PCR analysis to detect virulence factor g...

In 1995, we isolated a strain of Bacillus thuringiensis serotype H34 from severe human tissue necrosis. This bacterium was able to induce myonecrosis in immunosuppressed mice after cutaneous infection. Its potential pathogenicity for immunocompetent hosts was investigated in a mouse model of pulmonary infection. Mice infected intranasally by a suspension containing 10(8) spores died within 8 h in a clinical toxic-shock syndrome. In the same conditions, infection with a mutant without crystalline toxin, with the supernatant from a culture containing 10(8) bacteria ml(-1) and by the insecticidal strain serotypes 3a3b or H14 led to identical results. Lower inocula simply induced a local inflammatory reaction with bacterial persistence observed during the course of 10 days.